Ultrafast time-resolved fluorescence spectroscopy was applied to study physical properties of the phycobiliprotein R-phycoerythrin. R-phycoerythrin is a protein from the group of red algal bili-proteins. This protein has 2 types of chromophores: phycourobilin (PUB) and phycoerythrobilin (PEB). Radiationless interaction between PUB and PEP was examined under different conditions using one and two-photon excitation. The optical spectra of phycoerythrin 545 shows for types of behavior with temperature: forming a dimer at low temperature (10-20 C), partially dissociates to monomer at 40-50 C, nearly fully disordered at 60 C and at 70 disordered into ` and peptides .